View Single Post
  #26  
Old 01-26-2011, 08:57 PM
BallCoeff.435 BallCoeff.435 is offline
 
Join Date: Dec 2008
Location: God's Country
Posts: 749
Default

For a permanent (non-mobile) wood or dilute coal/wood mix heater, what you really, really want is a masonry heater or ridiculously heavy cast-iron one. (Or something similar, like a sealed steel stove embedded in masronry plates or bricks or water jacket.)

1.) You need something that will take fast, hot burns of wood and store the heat for gradual release over time. No smoldering fires choked down with some combination of dampers!

A small space gets overheated real quick with a hot fire, then gets cold fast after it burns down. If weight (mass) doesn't have to be towed around or broken down and packed, then it's your friend. Keep in mind though that anything in direct contact with a hot firebox, either a steel or firebrick one, has to be separated from that firebox by an expansion joint.

2.) You want an outside air feed so that warm inside air is not stolen by the stove just to feed the fire. Carbon monoxide protection is a nice plus too. Even an outside fuel and ash service would be good to cut down on mess.

3.) You want to keep the pipe straight up for best draft and easiest cleaning. Six-inch would be best.

4.) The pipe should NOT be considered a source of heat. Keep as much heat inside the pipe as possible (with an insulated pipe for example - even inside the building). That will avoid as many draft problems as possible, like fluttering flame jumping back into the room. Or like explosive fire-gas exuded from paper building up inside a cold stove at startup. You want the *difference* in temperature between the inside of the top of the chimney and the outside air to be as great as possible.

Stoves in a small room tend to be too hot anyway, you don't need even more of a problem from hot pipe metal.

It's different if you have a tent or big cabin or quonset hut with huge heat loss, equipped with a stove that's too small. In that case, you should just upgrade to a bigger stove and firebox, or several stoves, rather than trying to squeeze calories out of the pipe exhaust.
Reply With Quote